Japanese superstar Shohei Ohtani confirmed on Saturday he is joining the Los Angeles Dodgers in a record-breaking 10-year, US$700 million deal -- the richest contract in baseball history.

The future of the 29-year-old Los Angeles Angels ace had been the subject of intense speculation since the two-way star entered free agency at the end of the season.

Ohtani eventually opted for the Dodgers after a frenzied battle for his signature which also included interest from the Chicago Cubs, Toronto Blue Jays, New York Yankees and San Francisco Giants.

"To all the fans and everyone involved in the baseball world, I apologize for taking so long to come to a decision," Ohtani wrote on Instagram.

"I have decided to choose the Dodgers as my next team.

"I pledge to always do what's best for the team and always continue to give it my all to be the best version of myself.

"Until the last day of my playing career, I want to continue to strive forward not only for the Dodgers but for the baseball world," Ohtani added.

Ohtani's agent Nez Balelo said in a statement the deal would be worth $700 million over 10 years, shattering the record for the biggest contract in baseball history.

Balelo described Ohtani's mammoth payday as a "unique historic contract, for a unique historic player."

"Shohei is thrilled to be a part of the Dodgers organization," Balelo said. "He is excited to begin this partnership."

Ohtani has taken Major League Baseball by storm since landing in the league in 2018, with his almost unheard of combination of elite pitching and hitting prowess earning him comparisons to Babe Ruth.

Although his talents were not enough to help spark a revival in the Angels' fortunes - the team failed to make the playoffs following his arrival - Ohtani nevertheless dazzled in a flagging franchise.

He has twice been named American League Most Valuable Player, in 2021 and 2023, on both occasions winning by unanimous vote - the only player in history to achieve that distinction.

Although elbow injuries have cut short his pitching appearances - he missed the final month of the 2023 campaign with a torn ulnar collateral ligament in his elbow - this season was his most successful to date.

As a designated hitter, Ohtani led the AL in home runs with 44, in on-base percentage (.412), slugging percentage (.654) and total bases (325).

He hit 26 doubles and eight triples with 20 stolen bases and 95 runs-batted-in. He hit over .300 for the first time in his six-year major league career.

In 23 pitching starts he went 10-5 with a 3.14 earned-run-average and 167 strikeouts in 132 innings.

He had the lowest batting average against (.184) among all AL pitchers with at least 130 innings.

It marked Ohtani's second straight season with at least 10 wins on the mound and 10 home runs at the plate.

The only other player to accomplish that feat was New York Yankees legend Ruth back in 1918. (AFP)